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<h3><a name="SECTION00161411000000000000000"></a><a name="ctypes-loading-dynamic-link-libraries"></a>
<br>
14.14.1.1 Loading dynamic link libraries
</h3>

<p>
<code>ctypes</code> exports the <var>cdll</var>, and on Windows also <var>windll</var> and
<var>oledll</var> objects to load dynamic link libraries.

<p>
You load libraries by accessing them as attributes of these objects.
<var>cdll</var> loads libraries which export functions using the standard
<code>cdecl</code> calling convention, while <var>windll</var> libraries call
functions using the <code>stdcall</code> calling convention. <var>oledll</var> also
uses the <code>stdcall</code> calling convention, and assumes the functions
return a Windows <tt class="class">HRESULT</tt> error code. The error code is used to
automatically raise <tt class="class">WindowsError</tt> Python exceptions when the
function call fails.

<p>
Here are some examples for Windows, note that <code>msvcrt</code> is the MS
standard C library containing most standard C functions, and uses the
cdecl calling convention:
<div class="verbatim"><pre>
&gt;&gt;&gt; from ctypes import *
&gt;&gt;&gt; print windll.kernel32 # doctest: +WINDOWS
&lt;WinDLL 'kernel32', handle ... at ...&gt;
&gt;&gt;&gt; print cdll.msvcrt # doctest: +WINDOWS
&lt;CDLL 'msvcrt', handle ... at ...&gt;
&gt;&gt;&gt; libc = cdll.msvcrt # doctest: +WINDOWS
&gt;&gt;&gt;
</pre></div>

<p>
Windows appends the usual '.dll' file suffix automatically.

<p>
On Linux, it is required to specify the filename <em>including</em> the
extension to load a library, so attribute access does not work.
Either the <tt class="method">LoadLibrary</tt> method of the dll loaders should be used,
or you should load the library by creating an instance of CDLL by
calling the constructor:
<div class="verbatim"><pre>
&gt;&gt;&gt; cdll.LoadLibrary("libc.so.6") # doctest: +LINUX
&lt;CDLL 'libc.so.6', handle ... at ...&gt;
&gt;&gt;&gt; libc = CDLL("libc.so.6")     # doctest: +LINUX
&gt;&gt;&gt; libc                         # doctest: +LINUX
&lt;CDLL 'libc.so.6', handle ... at ...&gt;
&gt;&gt;&gt;
</pre></div>

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